Spin-on carbon compositions for lithographic processing

ABSTRACT

The invention described herein is directed towards spin-on carbon materials comprising polyamic acid compositions and a crosslinker in a solvent system. The materials are useful in trilayer photolithography processes. Films made with the inventive compositions are not soluble in solvents commonly used in lithographic materials, such as, but not limited to PGME, PGMEA, and cyclohexanone. However, the films can be dissolved in developers commonly used in photolithography. In one embodiment, the films can be heated at high temperatures to improve the thermal stability for high temperature processing. Regardless of the embodiment, the material can be applied to a flat/planar or patterned surface. Advantageously, the material exhibits a wiggling resistance during pattern transfer to silicon substrate using fluorocarbon etch.

RELATED APPLICATIONS

This is a divisional application of U.S. patent application Ser. No.13/648,890, filed Oct. 10, 2012, entitled SPIN-ON CARBON COMPOSITIONSFOR LITHOGRAPHIC PROCESSING, incorporated by reference herein. The '890application claims the priority benefit of a provisional applicationentitled SPIN-ON CARBON COMPOSITIONS FOR LITHOGRAPHIC PROCESSING, Ser.No. 61/545,313, filed Oct. 10, 2011, incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods of forming a carbon-rich(spin-on carbon) layer from a polyamic acid for use in a multilayerstack and the microelectronic structures thereof.

2. Description of the Prior Art

As the semiconductor industry continues to shrink the size of features,a single layer photoresist lacks sufficient thickness to completepattern transfer to a substrate. As a result, trilayer stacking(photoresist-hardmask-carbon layers) is typically used to transfer thepattern made by the photoresist to the substrate. The carbon layer canbe formed by chemical vapor deposition (CVD) or spin-coating. However,CVD processes are expensive, have low-throughput, and subject the waferto harsh conditions. Currently, epoxy cresol novolacs are the mostcommon material for fabrication of spin-on carbon (“SOC”) layers, butthis material has low thermal stability and low carbon content, leadingto high sublimation and poor wiggling resistance during pattern transferto silicon substrates. Additionally such a layer is difficult to removeafter curing. Other SOC layers have been formed that are removable bydry etching. However, drying etching requires harsh processingconditions and special equipment, making the process less thandesirable.

There is a need for improved SOC layers that exhibit high thermalstability and optical constants, while also being wet removable(developer soluble). Furthermore, these layers should prevent orminimize line “wiggling,” which is present in many prior art processes.

SUMMARY OF THE INVENTION

The present invention provides a method of forming a microelectronicstructure. The method comprises providing a substrate having a surface.Optionally, one or more intermediate layers are formed on the surface,there being an uppermost intermediate layer on the surface, if one ormore intermediate layers are present. A composition is applied to theuppermost intermediate layer, if present, or to the substrate surface,if no intermediate layers are present. The composition comprises apolyamic acid dissolved or dispersed in a solvent system. Thecomposition is heated to form a spin-on carbon or carbon-rich layer,with the carbon-rich layer being developer soluble, and exhibiting aweight loss of less than about 10% at a temperature of about 400° C. forabout 10 minutes.

The invention also provides a novel microelectronic structure. Thestructure comprises a microelectronic substrate having a surface andoptionally one or more intermediate layers on the surface. There is anuppermost intermediate layer on the surface, if one or more intermediatelayers are present. A carbon-rich layer is on the uppermost intermediatelayer, if present, or on the substrate surface, if no intermediatelayers are present. The carbon-rich layer: comprises a crosslinkedpolyamic acid; is developer soluble; and exhibits a weight loss of lessthan about 10% at a temperature of about 400° C. for about 10 minutes.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. (“FIG.”) 1 is a scanning electron microscope (“SEM”) photograph ofthe positive-tone development photolithography (40L/80P, 16.8 mJ)demonstrated in Example 26;

FIG. 2 is an SEM photograph of the negative-tone developmentphotolithography (53S/105P, 19.6 mJ) carried out in Example 27;

FIG. 3 is an SEM photograph of the etched, spin-on carbon layer formedin Example 28;

FIG. 4 shows the thermogravimetric analysis (“TGA”) curve of SOCformulation E-2 from Example 29;

FIG. 5 is an SEM photograph of SOC formulation E-2 filling isolated deepcontact hole, as described in Example 30;

FIG. 6 is an SEM photograph of SOC formulation E-2 filling dense deepcontact hole, as described in Example 30;

FIG. 7 is an SEM photograph showing an OptiStack® SOC110D pattern afterC₄F₈/Ar etching, as described in Example 32; and

FIG. 8 is an SEM photograph showing the pattern of Formulation E-2 afterC₄F₈/Ar etching, as described in Example 33.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Detailed DescriptionMethods of the Invention

In more detail, the present invention provides methods of formingmicroelectronic structures and is particularly suited for multilayerprocesses. In the inventive method, one or more optional intermediatelayers are applied to the surface of a substrate. Suitable intermediatelayers include those selected from the group consisting of spin-onhardmask, CVD hardmask, and spin-on carbon layers (without polyamicacids). Any conventional microelectronic substrate can be utilized.Preferred substrates include those selected from the group consisting ofsilicon, SiGe, SiO₂, Si₃N₄, SiON, aluminum, tungsten, tungsten silicide,gallium arsenide, germanium, tantalum, tantalum nitride, coral, blackdiamond, phosphorous or boron doped glass, Ti₃N₄, hafnium, HfO₂,ruthenium, indium phosphide, and mixtures of the foregoing. Thesubstrate surface can be planar, or it can include topography features(via holes, trenches, contact holes, raised features, lines, etc.). Asused herein, “topography” refers to the height or depth of a structurein or on a substrate surface.

A polyamic acid composition is applied to uppermost intermediate layer,if present, or to the substrate surface, if no intermediate layers arepresent, to form a layer on the substrate surface. The composition canbe applied by any known application method, with one preferred methodbeing spin-coating the composition at speeds of from about 500 rpm toabout 5,000 rpm (preferably from about 1,000 rpm to about 2,000 rpm) fora time period of from about 5 seconds to about 120 seconds (preferablyfrom about 30 seconds to about 60 seconds). After the composition isapplied, it is preferably heated to a temperature of from about 200° C.to about 450° C., and more preferably from about 205° C. to about 400°C. and for time periods of from about 10 seconds to about 120 seconds(preferably from about 30 seconds to about 90 seconds) to evaporatesolvents. Baking will initiate a crosslinking reaction to cure thelayer, thus forming the carbon-rich layer, which will comprise acrosslinked polyamic acid. The term “carbon-rich layer” as used herein,refers to layers comprising greater than about 50% by weight carbon,preferably greater than about 60% by weight carbon, more preferablygreater than about 70% by weight carbon, and even more preferably fromabout 70% to about 99% by weight carbon, based upon the weight of thelayer taken as 100% by weight. These carbon-rich layers will alsopreferably have a low hydrogen content (e.g., less than about 10% byweight hydrogen, preferably less than about 5% by weight hydrogen, morepreferably less than about 3% by weight hydrogen, and even morepreferably from about 0.010% to about 2% by weight hydrogen, based uponthe weight of the layer taken as 100% by weight).

The average thickness of the carbon-rich layer (determined after baking)is preferably from about 0.05 μm to about 10 μm, more preferably fromabout 0.1 μm to about 5.0 μm, and even more preferably from about 0.1 μmto about 2.0 μm. If the substrate surface includes topography, thecarbon-rich layer is preferably formed at a thickness sufficient tosubstantially cover the substrate topography and to achieve the aboveaverage thicknesses over the topography. The compositions used in theinventive methods exhibit excellent gap-fill properties and can filldeep contact holes very well.

Depending upon the exact polyamic acid composition used to form thecarbon-rich layer (discussed in more detail below), the dried orcrosslinked carbon-rich layer can have a refractive index (n value) ofat least about 1.40, preferably from about 1.45 to about 1.70, and morepreferably from about 1.50 to about 1.65 at the wavelength of use (e.g.,365 nm, 248 nm, 193 nm, 157 nm, or 13.5 nm).

The dried or crosslinked carbon-rich protective layer will besubstantially insoluble in typical organic solvents used to formsubsequent layers in the multilayer stack, such as propylene glycolmethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME),ethyl lactate, propylene glycol n-propyl ether, gamma-butyrolactone,cyclopentanone, cyclohexanone, n-butyl acetate, methyl isobutyl carbinol(MIBC), and mixtures thereof. Thus, when subjected to a stripping test,the carbon-rich layer will have a percent stripping of less than about5%, preferably less than about 1%, and more preferably about 0%. Thestripping test involves first determining the thickness by taking theaverage of measurements at five different locations of the layer. Thisis the initial average film thickness. Next, the film is rinsed with asolvent (e.g., ethyl lactate) for about 30 seconds, followed by spindrying at about 500-3,000 rpm for about 20-60 seconds to remove thesolvent. The thickness is measured again at those five points on thewafer using ellipsometry, and the average of these measurements isdetermined. This is the average final film thickness.

The amount of stripping is the difference between the initial and finalaverage film thicknesses. The percent stripping is:

${\%\mspace{14mu}{stripping}} = {\left( \frac{{amount}\mspace{14mu}{of}\mspace{14mu}{stripping}}{{initial}\mspace{14mu}{average}{\mspace{11mu}\;}{film}\mspace{14mu}{thickness}} \right) \times 100.}$

Although typically insoluble in organic solvents, the carbon-rich layeris soluble or capable of being rendered soluble in conventional aqueousdevelopers (e.g., photoresist developers). That is, the term“developer-soluble” as used herein means that the carbon-rich layer iscapable of being removed with conventional aqueous developers (e.g.,hydroxides and/or any alkaline/base chemistry solutions). Particularlypreferred developers are selected from the group consisting oftetramethyl ammonium hydroxide (TMAH), potassium hydroxide (KOH), sodiumhydroxide, and mixtures thereof. Thus, the carbon-rich layeradvantageously can be removed during processing without dry etching(e.g., reactive ion etching), and is preferably not subjected to any dryetching in the method of the invention.

The carbon-rich layer is preferably not photosensitive (i.e., a patterncannot be defined in the layer when it is exposed to about 1 J/cm²), andthus, photosensitive compositions such as photoresists or other imaginglayers are not suitable for use as carbon-rich layers of the invention.

Advantageously, the carbon-rich layer exhibits high thermal stability,making it particularly useful in high temperature processes such asdeposition of an inorganic mask by CVD. In this embodiment, thecrosslinked polyamic acid layer can be heated at a higher temperature(i.e., from about 300° C. to about 450° C., and preferably from about350° C. to about 400° C.) to promote imidization. The high thermalstability can be observed by TGA. Specifically, at a temperature ofabout 400° C. for about 10 minutes, the carbon-rich layer willexperience a weight loss of less than about 10%, preferably less thanabout 5%, and preferably about 0%.

The carbon-rich layers will also have low sublimation. At temperaturesof from about 205° C. to about 225° C., and following the sublimationtesting described in Example 31, carbon-rich layers according to theinvention will have a sublimation of less than about 1,500 ng,preferably less than about 1,000 ng, and even more preferably less thanabout 500 ng.

Finally, the carbon-rich layers form SOC patterns that minimize orprevent line deformation or line “wiggling.” Line wiggling isundesirable and prevents good pattern transfer to the underlaying layersand ultimately the substrate. Thus, improved patterning is achieved withthe present invention.

After formation of the carbon-rich layer on the substrate surface, oneor more additional intermediate layers can optionally be formed adjacent(i.e., on top of) the carbon-rich layer. Examples of such additionalintermediate layers include those selected from the group consisting ofetch block layers, pattern transfer layers, and photoresists. Theadditional intermediate layer can be formed by any known applicationmethod, with one preferred method being spin-coating at speeds of fromabout 1,000 to about 5,000 rpm (preferably from about from about 1,250to about 1,750 rpm) for a time period of from about 30 to about 120seconds (preferably from about 45 to about 75 seconds).

If an intermediate etch block layer is utilized, it preferably comprisescarbon compounds, metal compounds, or silicon compounds (e.g., Si₃N₄,SiO₂, SiC, or SiON). The thickness of the etch block layer will vary,but is preferably from about 0.1 nm to about 100 nm, more preferablyfrom about 1 nm to about 20 nm, and even more preferably from about 5 nmto about 10 nm.

The most preferred intermediate layer is a pattern transfer layer(hardmask) formed adjacent the carbon-rich layer. The pattern transferlayer can be formed by any known application method, with one preferredmethod being spin-coating at speeds of from about 1,000 to about 5,000rpm (preferably from about from about 1,000 to about 2,000 rpm) for atime period of from about 30 to about 120 seconds (preferably from about45 to about 60 seconds). Chemical vapor deposition can also be used toform the pattern transfer layer. The pattern transfer layer can then beheated to a temperature of from about 100° C. to about 300° C., and morepreferably from about 160° C. to about 205° C. and for a time period offrom about 30 seconds to about 120 seconds (preferably from about 45seconds to about 60 seconds) to evaporate solvents. The thickness of thepattern transfer layer after baking is preferably from about 1 nm toabout 1,000 nm, more preferably from about 20 nm to about 100 nm, andeven more preferably from about 30 nm to about 50 nm. Suitablecompositions for use in forming the pattern transfer layer includehardmask materials (e.g., silicon- or metal-containing hardmasks andhybrid hardmasks) or spin-on glass materials (e.g., silicates,phosphosilicates, siloxanes).

An imaging layer is then formed on the stack. The imaging layer can beformed by any known application method, with one preferred method beingspin-coating at speeds of from about 500 to about 5,000 rpm (preferablyfrom about from about 1,000 to about 2,000 rpm) for a time period offrom about 30 to about 120 seconds (preferably from about 45 to about 60seconds) onto the additional intermediate layers, if present, or ontothe carbon-rich layer, if no additional intermediate layers are present.The imaging layer is post-application baked at a temperature of at leastabout 90° C., and preferably from about 90° C. to about 130° C., fortime periods of from about 30 seconds to about 120 seconds (preferably45 to about 60 seconds). Suitable imaging compositions includecommercially-available photoresists (e.g., TArF Pi6-001 from TOK,Kawasaki shi, Kanagawa (Japan); ARX3001, ARX3340J, AM2073J, and KrFM592Yfrom JSR Micro, Sunnyvale, Calif.; SAIL-X-181, Shin-Etsu, Tokyo (Japan))or any other photosensitive compositions. The inventive methods permitthe use of much thinner imaging layers. The thickness of the imaginglayer is less than about 500 nm, preferably less than about 300 nm, morepreferably from about 50 nm to about 200 nm, and even more preferablyfrom about 100 nm to about 180 nm. It will be appreciated that aconventional anti-reflective coating could also be present in the stackbetween the additional intermediate layer (or carbon-rich layer, if noadditional intermediate level is present) and the imaging layer tocontrol reflection during exposure of the imaging layer.

The imaging layer can then be patterned by exposure to light of theappropriate wavelength. More specifically, the imaging layer is exposedusing a mask positioned above the imaging layer. The mask has open areasdesigned to permit radiation (hv) to pass through the mask and contactthe imaging layer. The remaining solid portions of the mask are designedto prevent radiation from contacting the imaging layer in certain areas.Those skilled in the art will readily understand that the arrangement ofopen areas and solid portions is designed based upon the desired patternto be formed in the imaging layer and ultimately in the substrate. Afterexposure, the imaging layer is preferably subjected to a post-exposurebake at a temperature of from about 90° C. to about 150° C., morepreferably from about 110° C. to about 130° C., for a time period offrom about 30 seconds to about 120 seconds.

Upon exposure, the portions of the imaging layer that are exposed toradiation are rendered soluble in aqueous developer. The exposedportions of the imaging layer that were made soluble by the aboveprocess are then contacted with an aqueous developer to remove theexposed portions to form the desired pattern in the imaging layer. Thepattern can be via holes, trenches, lines, spaces, etc., that willultimately be transferred to the substrate using an etch or ionimplantation process or metal deposition. Alternatively, the exposedportions of the imaging layer can be rendered insoluble during theexposure process, in which case, the removal process is reversed fromwhat is described above. That is, the unexposed portions are removedduring development to form the pattern. In either embodiment, at leastabout 95% of the exposed (or unexposed as the case may be) portions ofthe imaging layer will preferably be removed by the developer, morepreferably at least about 99%, and even more preferably about 100% willbe removed. Suitable developers are organic or inorganic alkalinesolutions such as KOH or TMAH, and preferably comprise an aqueoussolution of TMAH at a concentration of about 0.26N. Some of thesedevelopers are commercialized under the tradenames PD523AD (availablefrom Moses Lake Industries, Inc., Moses Lake, Wash.), MF-319 (availablefrom Shipley, Mass.), MF-320 (available from Shipley), and NMD3(available from TOK, Japan).

It will also be appreciated that other patterning methods may also beused, including emerging technologies, such as imprint lithography,nano-imprint lithography, hot embossing lithography, and stampingpattern transfer to form the pattern into imaging layer. Thesetechnologies use a patterned mold to transfer patterns instead ofrelying on photolithographic patterning, as described above. Directedself-assembly (DSA) could also be used to pattern the imaging layer.

Regardless of how the pattern is formed in the imaging layer, an etchingprocess is then used to transfer the pattern from the patterned imaginglayer into the pattern transfer layer and/or other additionalintermediate layer(s), if present. Preferably, RIE is used to transferthe pattern using a reactive ion plasma of CF₄, CHF₃, O₂, HBr, Cl₂, SF₆,C₂F₆, C₄F₈, CO, CO₂, N₂, H₂, C₄H₈, Ar, N₂H₂, He, CH₂F₂, or a mixturethereof. Etching breaks through the additional intermediate layer(s) andexposes the developer-soluble, carbon-rich layer. The pattern is thentransferred into the carbon-rich layer.

Polyamic Acid Compositions for Use in the Invention

The carbon-rich compositions utilized will comprise a polyamic aciddispersed or dissolved in a solvent system. The polyamic acid ispreferably present in the composition at a level of from about 1% toabout 30% by weight, preferably from about 2% to about 20% by weight,and more preferably from about 5% to about 15% by weight, based upon thetotal weight of solids in the composition taken as 100% by weight. Theweight average molecular weight of the polyamic acid will preferably beless than about 15,000 Daltons, more preferably from about 4,000 Daltonsto about 12,000 Daltons, and even more preferably from about 6,000Daltons to about 11,000 Daltons.

The polyamic acid should be selected to be a highly rigid structure.Ideally, the polyamic acid will have a flat or planar structure withlimited spinning possible and a good deal of n bonding. The synthesis ofthese polyamic acids and suitable developer-soluble compositionscomprising these polymers is described in U.S. Pat. Nos. 7,261,997 and7,364,835, incorporated by reference herein in their entirety. Thepolyamic acids can be formed by adjusting the dianhydride-to-diamineratio as well as the dianhydride and diamine types. The dianhydride canbe aliphatic or aromatic. Typical aliphatic dianhydrides include thoseselected from the group consisting of5-(2,5-dioxotetrahydrol)-3-methyl-3-cyclohexene-1,2-dicarboxylic acidanhydride, cyclobutane tetracarboxylic dianhydride,1,2,3,4-cyclopentanetetracarboxylic acid dianhydride,tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride,4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylicanhydride, and bicyclo(2,2,2)oct-7-ene-2,3,5,6-tetracarboxylicdianhydride. Aromatic dianhydrides include those selected from the groupconsisting of 3,3′,4′-benzophenone tetracarboxylic acid dianhydride(BTDA), pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyltertracarboxylic dianhydride (s-BPDA), 2,2′-bis-(3,4-dicarboxy phenyl)hexafluoropropane dianhydride (6FDA), 4,4′-oxydiphthalic anhydride(OPDA), 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride (DSDA),4,4′-bisphenol A dianhydride (BPADA), hydroquinone diphtatic anhydride(HQDA), 3,4,9,10-perylene-tetracarboxylic dianhydride,1,4,5,8-naphthalenetetracarboxylic dianhydride, and ethylene glycolbis(trimellitic anhydride).

The diamine can also be aliphatic or aromatic. Typical aliphaticdiamines include those selected from the group consisting of1,3-bis(aminomethyl)-cyclohexane, 1,4-bis(aminimethyl)-cyclohexane,4,4′-methylenebis(cyclohexylamine), and 4,4′-methylenebis(2-methylcyclohexyl)amine. Aromatic diamines include those selectedfrom the group consisting of 3-aminobenzylamine,1,3-bis(3-aminophenoxy)-benzene, 1,3-bis(4-aminophenoxy)-benzene,1,4-bis(4-aminophenoxy)benzene, 4,4′-bis(4-aminophenoxy)-biphenyl,2,2-bis[4-4-aminophenoxy)-phenyl]hexafluproprane,bis[4-(4-aminophenoxy)-phenyl]propane,bis[4-(4-aminophenoxy)-phenyl]sulfone,bis[4-(4-aminophenoxy)-phenyl]sulfone,1,1′-bis(4-aminophenyl)-clohexane, 9,9′-bis(4-aminophenyl)-fluorene(FDA), 2,2′-bis(4-aminophenyl)-hexafluoropropane,bis(2-aminophenyl)sulfide, bis(4-aminophenyl)sulfide,bis(3-aminophenyl)sulfone, bis(4-aminophenyl)sulfone,4,4′-diamino-3,3′-dimethyl-diphenylmethane, 3,4′-diaminodiphenyl ether,4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl methane,3,4′-diaminodiphenyl methane, 2,7-diaminofluorene,1,5-diaminonaphthalene, 4,4′-diaminooctafluorobiphenyl,2,5-dimethyl-1,4-phenylenediamine, 4,4′-ethylenedianiline,1,3-phenylenediamine, 1,4-phenylenediamine,2,3,5,6-tetramethyl-1,4-phenylenediamine, m-xylylenediamine, andp-xylylenediamine.

Preferred polyamic acids include recurring monomers having the formulas

where each of

is individually selected from the group consisting of aliphatic and arylgroups. Particularly preferred X and Y groups include those selectedfrom the group consisting of substituted and unsubstituted phenyl,biphenyl, naphthyl, and anthryl groups, and substituted andunsubstituted C₁-C₂ aliphatic (preferably alkyl) groups.

Particularly preferred polyamic acids for use in the compositioncomprise recurring monomers selected from the group consisting of

where:

X is selected from the group consisting of —O—, —S—, —CH₂—, —C(CF₃)₂—,and —C(CH₃)₂—;

n is 2-8; and

each R is individually selected from the group consisting of —H and —OH.

The preferred molar ratio of dianhydrides to diamines is from about1.8:1 to about 1.05:1, more preferably from about 1.6:1 to about 1.1:1,and even more preferably from about 1.4:1 to about 1.2:1.

The polyamic acid is also selected to be “carbon-rich.” The term“carbon-rich polyamic acid” as used herein, refers to polyamic acidshaving greater than about 50% by weight carbon, preferably greater thanabout 60% by weight carbon, more preferably greater than about 70% byweight carbon atoms, and even more preferably from about 70% to about99% by weight carbon, based upon the total weight of the polymer takenas 100% by weight. The preferred polyamic acid will also preferably havea low hydrogen content (e.g., less than about 10% by weight hydrogen,preferably less than about 5% by weight hydrogen, more preferably lessthan about 3% by weight hydrogen, and even more preferably from about0.01% to about 2% by weight hydrogen, based upon the total weight of thepolymer taken as 100% by weight).

The carbon-rich compositions used in the invention also preferablyinclude a crosslinking agent that will react with the carboxylic acidand/or the secondary amine. Epoxy crosslinking agents, vinyl ethercrosslinking agents, and amino crosslinking agents are particularlypreferred. Epoxy crosslinking agents include small molecules withmultiple epoxy groups such as those selected from the group consistingof N,N,N′,N′-tetraglycidyl-4,4′-methylenebisbenzenamine,4-glycidyloxy-N,N′-diglycidylaniline and bis(3,4-epoxy cyclo hexylmethyl)adipate, and polymers with epoxy groups, such as epoxy cresolnovolac or polymers prepared from methylacrylate or acrylates with epoxygroups as side chains. Vinyl ether crosslinkers include multi functionalvinyl ethers, such as those selected from the group consisting of1,3,5-benzenetricarboxylic acid tris[4-(ethenyloxy)butyl]ester,bis[4-(vinyloxy)butyl]isophthalate,bis[4-(vinyloxy)butyl]1,6-hexanediylbiscarbamate,bis[4-(vinyloxymethyl)cyclohexylmethyl]glutarate,bis[4-(vinyloxy)butyl]succinate, tri(ethylene glycol)divinyl ether, andpoly(ethylene glycol)divinyl ether. Amino resin crosslinkers includethose selected from the group consisting of melamine crosslinkers, ureacrosslinkers, benzoguanamine crosslinkers, and glycoluril crosslinkers.

The crosslinking agent is preferably present in the composition at alevel of from about 0.1% to about 30% by weight, preferably from about0.5% to about 25% by weight, and more preferably from about 1% to about20% by weight, based upon the total weight of solids in the compositiontaken as 100% by weight.

A number of optional ingredients can also be included in the composition(e.g., catalysts, surfactants). Optional catalysts may include, but arenot limited to, acids, such as 5-sulfosalicylic acid, thermallygenerated acid (TAG), photo generated acid (PAG), or base. Suitablesurfactants include both ionic or nonionic surfactants.

Regardless of the embodiment, the compositions are formed by simplydispersing or dissolving the polyamic acid in a suitable solvent system,preferably at ambient conditions and for a sufficient amount of time toform a substantially homogeneous dispersion. The other ingredients(e.g., crosslinker, any catalysts and/or surfactants) are preferablydispersed or dissolved in the solvent system along with the compound.

Preferred solvent systems include a solvent selected from the groupconsisting of PGMEA, PGME, propylene glycol n-propyl ether (PnP), ethyllactate, cyclohexanone, gamma butyrolactone (GBL), and mixtures thereof.The solvent system should be utilized at a level of from about 80-99% byweight, and preferably from about 95-99% by weight, based upon the totalweight of the composition taken as 100% by weight. Thus, thecompositions typically have a solids content of from about 1-20% byweight, and preferably from about 1-5% by weight, based upon the totalweight of the composition taken as 100% by weight.

The resulting polyamic acid compositions will be carbon-rich.“Carbon-rich compositions” as used herein refers to compositionscomprising greater than about 50% by weight carbon, preferably greaterthan about 60% by weight carbon, more preferably greater than about 70%by weight carbon, and even more preferably from about 70% to about 99%by weight carbon, based upon the total solids in the composition takenas 100% by weight. These polyamic acid compositions will also preferablyhave a low hydrogen content (e.g., less than about 10% by weighthydrogen, preferably less than about 5% by weight hydrogen, morepreferably less than about 3% by weight hydrogen, and even morepreferably from about 0.01% to about 2% by weight hydrogen, based uponthe total solids in the composition taken as 100% by weight).

EXAMPLES

The following examples set forth preferred methods in accordance withthe invention. It is to be understood, however, that these examples areprovided by way of illustration and nothing therein should be taken as alimitation upon the overall scope of the invention.

Example 1 Synthesis of Polymer A

In this Example, 16.99 grams (0.0643 mole) of5-(2,5′-dioxotetrahydrol)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride (CHRISKEV, Inc., Lenexa, Kans.), 14.00 grams (0.0402 mole) of4,4′-(9-fluorenylidene)dianiline (CHRISKEV, Inc., Lenexa, Kans.), and123.95 grams of propylene glycol monomethyl ether (“PGME,” Ultra PureSolutions, Inc., Castroville, Calif.) were added to a two-necked roundflask. The contents of the flask were stirred under nitrogen and, whilestirring was maintained, heated at 60° C. for 24 hours to complete thereaction. The mixture was allowed to cool to room temperature and wasbottled. Solids content was 20% by weight. The reaction scheme of thisExample is shown below.

Example 2 SOC Formulation A-1

An SOC formulation was prepared by mixing 5.01 grams of Polymer A fromExample 1 with 0.114 gram of a 50% by weight solution of MY-720(Huntsman Advanced Materials, Woodlands, Tex.) in PGME, 22.04 grams ofPGME, and 2.92 grams of cyclohexanone to make a solution having a solidscontent of 3.5% by weight. The solution was mixed well for 4 hours andwas filtered through a PTFE filter having a pore size of 0.1 μm. Theformulation was spin-coated onto a 4-inch silicon wafer at 1,500 rpm for60 seconds and then was baked on a hot plate at 225° C. for 60 seconds.The resulting cured film was measured by ellipsometry to be 1317 Å thickand could not be removed by PGME or propylene glycol methyl etheracetate (“PGMEA”).

Example 3 SOC Formulation A-2

An SOC formulation was prepared by mixing 5.01 grams of Polymer A fromExample 1 with 0.206 gram of a 50% by weight solution of MY-720 in PGME,23.25 grams of PGME, and 3.07 grams of cyclohexanone to make a solutionhaving a solids content of 3.5% by weight. The solution was mixed wellfor 4 hours and then was filtered through a PTFE filter having a poresize of 0.1 μm. The formulation was spin-coated onto a 4-inch siliconwafer at 1,500 rpm for 60 seconds, and then was baked on a hot plate at205° C. for 60 seconds. The resulting cured film was measured byellipsometry to be 1,378 Å thick and could not be removed by PGME orPGMEA.

Example 4 Synthesis of Polymer B

In this Example, 15.92 grams (0.0603 mole) of5-(2,5′-dioxotetrahydrol)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride, 15.00 grams (0.043 mole) of 4,4′-(9-fluorenylidene)dianiline,and 123.95 grams of PGME (Ultra Pure Solutions, Inc., Castroville,Calif.) were added to a two-necked round flask. The contents werestirred under nitrogen and, while stirring was maintained, heated at 60°C. for 24 hours to complete the reaction. The mixture was allowed tocool to room temperature and was bottled. The solids content was 20% byweight. The reaction scheme is the same as that shown in Example 1.

Example 5 SOC Formulation B-1

An SOC formulation was prepared by mixing 5.01 grams of Polymer B fromExample 4 with 0.101 gram of a 50% by weight solution of MY-720 in PGME,22.03 grams of PGME, and 2.92 grams of cyclohexanone to make a solutionhaving a solids content of 3.5% by weight. The solution was mixed wellfor 4 hours and was filtered through a PTFE filter having a pore size of0.1 μm. The formulation was spin-coated onto a 4-inch silicon wafer at1,500 rpm for 60 seconds and then was baked on a hot plate at 205° C.for 60 seconds. The resulting cured film was measured by ellipsometry tobe 1423 Å thick and was unable to be removed by PGME and PGMEA.

Example 6 SOC Formulation B-2

An SOC formulation was prepared by mixing 5.02 grams of Polymer B fromExample 4 with 0.202 gram of a 50% by weight solution of MY-720 in PGME,23.22 grams of PGME, and 3.03 grams of cyclohexanone to make a solutionhaving a solids content of 3.5% by weight. The solution was mixed wellfor 4 hours and was filtered through a PTFE filter having a pore size of0.1 μm. The formulation was spin-coated onto a 4-inch silicon wafer at1,500 rpm for 60 seconds and then was baked on a hot plate at 205° C.for 60 seconds. The resulting cured film was measured by ellipsometry tobe 1,422 Å thick and could not be removed by PGME and PGMEA.

Example 7 Synthesis of Polymer C

In this Example, 20.40 grams (0.0459 mole) of4,4′-(hexafluoroisopropylidene)diphthalic anhydride (CHRISKEV, Inc.,Lenexa, Kans.), 10.00 grams (0.0287 mole) of4,4′-(9-fluorenylidene)dianiline, and 121.70 grams of PGME were added toa two-necked round flask. The contents of the flask were stirred undernitrogen and, while stirring was maintained, heated to 60° C. for 20hours to complete the reaction. The mixture was allowed to cool to roomtemperature and was bottled. The solids content was 20% by weight. Thereaction scheme is the same as that shown in Example 1.

Example 8 SOC Formulation C-1

An SOC formulation was prepared by mixing 9.08 grams of Polymer C fromExample 7 with 0.36 gram of a 50% by weight solution of MY-720 in PGME,35.75 grams of PGME, and 7.80 grams of cyclohexanone to make a solutionhaving a solids content of 3.5% by weight. The solution was mixed wellfor 4 hours and was filtered through a PTFE filter having a pore size of0.1 μm. The formulation was spin-coated onto a 4-inch silicon wafer at1,500 rpm for 60 seconds and then was baked on a hot plate at 205° C.for 60 seconds. The resulting cured film was measured by ellipsometry tobe 1,578 Å thick and could not be removed by PGME and PGMEA.

Example 9 Synthesis of Polymer D

In this Example, 16.99 grams (0.0643 mole) of5-(2,5′-dioxotetrahydrol)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride, 14.0 grams (0.0402 mole) of 4,4′-(9-fluorenylidene)dianiline, and 99.2 grams of PGME and 24.8 grams of cyclohexanone (UltraPure Solutions, Inc., Castroville, Calif.) were added to a two-neckedround flask. The contents of the flask were stirred under nitrogen and,while stirring was maintained, heated at 60° C. for 24 hours to completethe reaction. The mixture was allowed to cool to room temperature andwas bottled. Solids content was about 20% by weight. The reaction schemeis the same as that shown in Example 1.

Example 10 SOC Formulation D-1

An SOC formulation was prepared by mixing 5.01 grams of Polymer D fromExample 9 with 0.15 gram of a 50% by weight solution of MY-721 (HuntsmanAdvanced Materials, Woodlands, Tex.) in PGME, and 15.5 grams of PGME.The solution was mixed well for 4 hours and was filtered through a PTFEfilter having a pore size of 0.1 μm. The formulation was spin-coatedonto a 4-inch silicon wafer for 60 seconds and then was baked on a hotplate at 205° C. for 60 seconds.

Example 11 Synthesis of Polymer E

In this Example, 15.9 grams (0.0609 mole) of5-(2,5′-dioxotetrahydrol)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride, 15.00 grams (0.0430 mole) of4,4′-(9-fluorenylidene)dianiline, 98.8 grams of PGME, 24.8 gramscyclohexanone were added to a two-necked round flask. The contents ofthe flask were stirred under nitrogen and, while stirring wasmaintained, heated at 60° C. for 24 hours to complete the reaction. Themixture was allowed to cool to room temperature and was bottled. Solidscontent was about 20% by weight. The reaction scheme is the same as thatshown in Example 1.

Example 12 SOC Formulation E-1

An SOC formulation was prepared by mixing 5.01 grams of Polymer E fromExample 11 with 0.15 gram of a 50% by weight solution of MY-721 in PGMEand 15.5 grams of PGME. The solution was mixed well for 4 hours and wasfiltered through a PTFE filter having a pore size of 0.1 μm. Theformulation was spin-coated onto a 4-inch silicon wafer for 60 secondsand then was baked on a hot plate at 205° C. for 60 seconds.

Example 13 SOC Formulation E-2

An SOC formulation was prepared by mixing 5.01 grams of Polymer E fromExample 11 with 0.20 gram 1,3,5-benzenetricarboxylic acidtris[4-(ethenyloxy)butyl]ester crosslinker (structure shown below,Brewer Science Inc., Rolla, Mo.) and 15.5 grams of PGME. The solutionwas mixed well for 4 hours and was filtered through a PTFE filter havinga pore size of 0.1 μm. The formulation was spin-coated onto a 4-inchsilicon wafer for 60 seconds and then was baked on a hot plate at 225°C. for 60 seconds.

Example 14 SOC Formulation E-3

An SOC formulation was prepared by mixing 5.01 grams of Polymer E fromExample 11 with 0.20 gram Cymel 1174 crosslinker (structure shown below,Cytech Industries, Woodland Park, N.J.), 0.01 g TAG 2689 (thermal acidgenerator from King Industries, Norwalk, Conn.) in PGME, and 15.5 gramsof PGME. The solution was mixed well for 4 hours and was filteredthrough a PTFE filter having a pore size of 0.1 μm. The formulation wasspin-coated onto a 4-inch silicon wafer for 60 seconds and then baked ona hot plate at 205° C. for 60 seconds.

Example 15 Synthesis of Polymer F

In this procedure, 14.57 grams (0.0551 mole) of5-(2,5′-dioxotetrahydrol)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride, 15.00 grams (0.0459 mole) of4,4′-(9-fluorenylidene)dianiline, 98.8 grams of PGME, and 24.8 gramscyclohexanone were added to a two-necked round flask. The contents ofthe flask were stirred under nitrogen and, while stirring wasmaintained, were heated at 60° C. for 24 hours to complete the reaction.The mixture was allowed to cool to room temperature and was bottled.Solids content was about 20% by weight. The reaction scheme is the sameas that shown in Example 1.

Example 16 SOC Formulation F-1

An SOC formulation was prepared by mixing 5.01 grams of Polymer F fromExample 15 with 0.15 gram of a 50% by weight solution of MY-721 in PGMEand 15.5 grams of PGME. The solution was mixed well for 4 hours and wasfiltered through a PTFE filter having a pore size of 0.1 μm. Theformulation was spin-coated onto a 4-inch silicon wafer for 60 secondsand then was baked on a hot plate at 205° C. for 60 seconds.

Example 17 Synthesis of Polymer G

In this procedure, 15.9 grams (0.0609 mole) of5-(2,5′-dioxotetrahydrol)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride, 15.00 grams (0.0430 mole) of4,4′-(9-fluorenylidene)dianiline, 24.8 grams of PGME, and 98.8 gramscyclohexanone were added to a two-necked round flask. The contents ofthe flask were stirred under nitrogen and, while stirring wasmaintained, were heated at 60° C. for 24 hours to complete the reaction.The mixture was allowed to cool to room temperature and was bottled.Solids content was about 20% by weight. The reaction scheme is the sameas that shown in Example 1.

Example 18 Synthesis of Polymer H

In this procedure, 19.6 grams (0.0441 mole) of4,4′-(hexafluoroisopropylidene)diphthalic anhydride (CHRISKEV, Inc.,Lenexa, Kans.), 11.00 grams (0.0315 mole) of4,4′-(9-fluorenylidene)dianiline, 85.79 grams of PGME, and 36.75 gramsof cyclohexanone were added to a two-necked round flask. The contents ofthe flask were stirred under nitrogen and, while stirring wasmaintained, were heated to 80° C. for 20 hours to complete the reaction.The mixture was allowed to cool to room temperature and was bottled. Thesolids content was 20% by weight. The reaction scheme is shown below.

Example 19 SOC Formulation H-1

An SOC formulation was prepared by mixing 5.01 grams of Polymer II fromExample 18 with 0.05 gram of a 50% by weight solution of MY-721(Huntsman Advanced Materials) in PGME, and 15.5 grams of PGME. Thesolution was mixed well for 4 hours and was filtered through a PTFEfilter having a pore size of 0.1 μm. The formulation was spin-coatedonto a 4 inch silicon wafer for 60 seconds and then was baked on a hotplate at 350° C. for 60 seconds. The highly thermal stable carbon layerformed according to the scheme shown below.

Example 20 Synthesis of Polymer I

In this Example, 19.6 grams (0.0441 mole) of4,4′-(hexafluoroisopropylidene)diphthalic anhydride, 11.00 grams (0.0315mole) of 4,4′-(9-fluorenylidene)dianiline, and 121.70 grams ofgamma-butyrolactone (GBL) were added to a two-necked round flask. Thecontents of the flask were stirred under nitrogen and, while stirringwas maintained, were heated to 80° C. for 20 hours to complete thereaction. The mixture was allowed to cool to room temperature and wasbottled. The solids content was 20% by weight. The reaction scheme isthe same as that shown in Example 18.

Example 21 Synthesis of Polymer J

In this Example, 11.3 grams (0.0351 mole) of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (CHRISKEV, Inc., Lenexa, Kans.), 8.71 grams(0.0251 mole) of 4,4′-(9-fluorenylidene)dianiline, 56.0 grams of PGME,and 24.0 grams of cyclohexanone were added to a two-necked round flask.The contents of the flask were stirred under nitrogen and, whilestirring was maintained, heated to 80° C. for 20 hours to complete thereaction. The mixture was allowed to cool to room temperature and wasbottled. The solids content was 20% by weight. The reaction scheme isshown below.

Example 22 SOC Formulation J-1

An SOC formulation was prepared by mixing 5.01 grams of Polymer J fromExample 21 with 0.15 gram of a 50% by weight solution of MY-721 in PGMEand 15.5 grams of PGME. The solution was mixed well for 4 hours and wasfiltered through a PTFE filter having a pore size of 0.1 μm. Theformulation was spin-coated onto a 4-inch silicon wafer at 1,500 rpm for60 seconds and then was baked on a hot plate at 205° C. for 60 seconds.

Example 23 Synthesis of Polymer K

In this procedure, 7.93 grams (0.0363 mole) of pyromelitic dianhydride(CHRISKEV, Inc., Lenexa, Kans.), 12.07 grams (0.0260 mole) of4,4′-(9-fluorenylidene)dianiline, 56.0 grams of PGME, and 24.0 grams ofcyclohexanone were added to a two-necked round flask. The contents ofthe flask were stirred under nitrogen and, while stirring wasmaintained, heated to 80° C. for 20 hours to complete the reaction. Themixture was allowed to cool to room temperature and was bottled. Thesolids content was 20% by weight. The reaction scheme is shown below.

Example 24 SOC Formulation K-1

An SOC formulation was prepared by mixing 5.01 grams of Polymer K fromExample 23 with 0.15 gram of a 50% by weight solution of MY-721 in PGMEand 15.5 grams of PGME. The solution was mixed well for 4 hours and wasfiltered through a PTFE filter having a pore size of 0.1 μm. Theformulation was spin-coated onto a 4-inch silicon wafer at 1500 rpm for60 seconds and then was baked on a hot plate at 205° C. for 60 seconds.

Example 25 Characterization of SOC Formulations

The optical constants (n and k) and film thickness were measured byM2000 Ellipsometer (J. A. Woollam, Lincoln, Nebr.). For the solventresistance test, the coated wafer was puddled with the solvent for 20seconds and spin-dried. The thickness before and after solvent contactwas compared, and the results are listed in Table 1. For the reworkingtest, the coated wafer was immersed in the developer PD523AD (MosesChemicals Inc., Moses Lake, Wash.) at different temperatures for fiveminutes, and then rinsed by deionized water.

TABLE 1 Example 2 Example 3 Example 5 Example 6 Example 8 Example 10(SOC (SOC (SOC (SOC (SOC (SOC Formulation Formulation FormulationFormulation Formulation Formulation A-1) A-2) B-1) B-2) C-1) D-1)Optical n_(193 nm) 1.56 1.55 1.55 1.56 1.56 Constants k_(193 nm) 0.450.46 0.46 0.44 0.45 n_(633 nm) 1.61 1.62 1.62 1.61 1.61 k_(633 nm) 0.000.00 0.00 0.00 0.00 Stripping Loss in 0.0% 0.08%  25% 0.08% 0.3% 0.0%Loss PGME Loss in 0.0%  0.0% 0.0%  0.0% 0.0% 0.0% PGMEA Rework ReworkClean Residue NA Residue No Clean at room temp. Rework Residue ResidueResidue Residue Clean at 60° C. Example 12 Example 13 Example 14 Example16 Example 22 Example 24 (SOC (SOC (SOC (SOC (SOC (SOC FormulationFormulation Formulation Formulation Formulation Formulation E-1) E-2)E-3) F-1) J-1) K-1) Optical n_(193 nm) 1.55 1.55 1.56 1.56 Constantsk_(193 nm) 0.46 0.46 0.44 0.44 n_(633 nm) 1.62 1.62 1.61 1.61 k_(633 nm)0.00 0.00 0.00 0.00 Stripping Loss in 0.00% 0.0% 0.0% 0.0% 0.0% 0.0%Loss PGME Loss in  0.0% 0.0% 0.0% 0.0% 0.0% 0.0%) PGMEA Rework ReworkClean No Clean No Clean Clean at room temp. Rework Clean Clean at 60° C.

Example 26 Positive-Tone Development Lithography

A lithography test was performed using the following multilayer stack(from top to bottom): AIM54B4 (JSR Micro. Inc., Sunnyvale, Calif.)photoresist, OptiStack® HM9825 (Brewer Science Inc., Rolla, Mo.)hardmask, and SOC Formulation E-2 (Example 13) as the carbon layer. Thecoated wafer was exposed using a 1900i stepper (ASML, Veldhoven,Netherlands) and developed by an aqueous basic solution, OPD5262(FujiFilm, North Kingstown, R.I.) to remove the exposed section. FIG. 1demonstrates the lithography results.

Example 27 Negative-Tone Development Lithography

A lithography test was performed using the following stacking from thetop to bottom: FAIRS9521-V10K (FujiFilm, North Kingstown, R.I.)photoresist; an experimental hardmask from Brewer Science Inc., Rolla,Mo.; and SOC Formulation E-2 (Example 13) as the carbon layer. Thecoated wafer was exposed using a 1900i stepper and developed using anorganic developer, FN-DP001 (FujiFilm, North Kingstown, R.I.), to removeunexposed section. FIG. 2 demonstrates the lithography results.

Example 28 Pattern Transfer to SOC Layer

The wafer from Example 26 was cut into chips and then loaded at OxfordPlasmalab RIE for etching at following conditions: CF₄, 35 sccm, 55 s,50 mTorr, 100 W, followed by Ar/CO₂, 25/25 sccm, 70 s, 20 mTorr, 300 W.The SEM photograph (FIG. 3) demonstrated that the pattern of thephotoresist was transferred to the SOC layer successfully.

Example 29 Thermal Stability of the SOC

A film of Formulation E-2 (Example 13) was formed on a wafer and thenwas peeled from wafer and loaded into a TGA pan. The sample was heatedto 400° C. at a speed of 20° C./min, and held for 10 minutes. FIG. 4shows the curve of weight loss vs. time, which indicated that materialexhibited an extremely high thermal stability at that temperature,similar to the temperatures at which CVD processes are carried out todeposit hardmasks on the SOC layer.

Example 30 Gap Filling

SOC Formulations E-2 (Example 13) and E-3 (Example 14) were spin-coatedon chips cut from Topowafer (SEMATECH, Albany, N.Y.) and baked at 225°C. SEM pictures (FIGS. 5 and 6) demonstrate that deep contact holes(dense or isolated) are filled very well without any defects.

Example 31 Sublimation Testing

Quartz crystal microbalance (QCM) was used to determined the sublimationof samples. In this method, a quartz crystal is suspended over a hotplace, where it can collect the outgassed material from heated wafer. Aventilation line is attached at the top to draw air flow upwards andallow the outgassed material to condense on the surface of the quartzcrystal. The condensate is collected on the crystal, and the change inresonant frequency is correlated to mass units of the condensate. Thestandard process includes a 4-inch silicon wafer coated with an organicspin-on coating. The wafer was placed under the QCM on a hot place for120 seconds. The data are collected.

OptiStack® SOC110D (Brewer Science, Rolla, Mo.), Formulation E-1(Example 12), and Formulation E-2 (Example 13) were spin-coated on a4-inch silicon wafer and baked. The sublimation was collected for 120seconds. The data are listed in Table 2, which demonstrated that theformulation exhibited comparable sublimation to current standardproducts, even when the baking temperature was higher.

TABLE 2 Sample Bake Temperature Sublimation (ng) OptiStack ® SOC110D205° C. 1231 Formulation E-1 205° C. 385 Formulation E-2 225° C. 1392

Example 32 Pattern Transfer to Silicon Substrate and Wiggling Resistance(Test 1)

A lithography test was performed using the following multilayer stack(from top to bottom): AIM54B4 photoresist, OptiStack® HM825 hardmask,and OptiStack® SOC 110D as the carbon layer. The coated wafer wasexposed using a 1900i stepper and developed by OPD5262 to remove theexposed section. The wafer was cut into chips and then loaded into anOxford Plasmalab RIE for etching at following conditions: CF₄, 35 sccm,55 s, 50 mTorr, 100 W, followed by Ar/CO₂, 25/25 sccm, 70 s, 20 mTorr,300 W, and then C₄F₈/Ar, 5/100 sccm, 70 s, 20 mTorr, 300 W. FIG. 7 showsthat the pattern of SOC layer wiggled during C₄F₈/Ar etching, and therewas no good pattern transfer to silicon substrate.

Example 33 Pattern Transfer to Silicon Substrate and Wiggling Resistance(Test 2)

The wafer from Example 26 was cut into chips and then loaded into anOxford Plasmalab RIE for etching at following conditions: CF₄, 35 sccm,55 s, 50 mTorr, 100 W, followed by Ar/CO₂, 25/25 sccm, 70 s, 20 mTorr,300 W, and the C₄F₈/Ar, 5/100 sccm, 70 s, 20 mTorr, 300 W. FIG. 8 showsthat the SOC pattern did not wiggle, which exhibited better wigglingresistance than current standard materials (Example 32). The pattern wastransferred to the silicon substrate successfully.

We claim:
 1. A microelectronic structure comprising: a microelectronicsubstrate having a surface; optionally one or more intermediate layerson said substrate surface, there being an uppermost intermediate layeron said substrate surface, if one or more intermediate layers arepresent; a carbon-rich layer on said uppermost intermediate layer, ifpresent, or on said substrate surface, if no intermediate layers arepresent, said carbon-rich layer: comprising a crosslinked polyamic acid;being developer soluble; and exhibiting a weight loss of less than about10% at a temperature of about 400° C. for about 10 minutes.
 2. Thestructure of claim 1, there being at least one intermediate layer onsaid substrate surface.
 3. The structure of claim 1, further comprisingan imaging layer on said carbon-rich layer.
 4. The structure of claim 1,further comprising at least one additional intermediate layer on saidcarbon-rich layer.
 5. The structure of claim 4, further comprising animaging layer on said at least one additional intermediate layer.
 6. Thestructure of claim 1, wherein said carbon-rich layer comprises greaterthan about 50% by weight carbon, based upon the weight of the layertaken as 100% by weight.
 7. The structure of claim 1, wherein saidcarbon-rich layer comprises less than about 10% by weight hydrogen,based upon the weight of the layer taken as 100% by weight.
 8. Thestructure of claim 1, wherein said microelectronic substrate is selectedfrom the group consisting of silicon, SiGe, SiO₂, Si₃N₄, SiON, aluminum,tungsten, tungsten silicide, gallium arsenide, germanium, tantalum,tantalum nitride, coral, black diamond, phosphorous or boron dopedglass, Ti₃N₄, hafnium, HfO₂, ruthenium, indium phosphide, and mixturesof the foregoing.
 9. The structure of claim 1, wherein said carbon-richlayer has an n value of at least about 1.40.
 10. The structure of claim1, wherein said crosslinked polyamic acid is formed from a polyamic acidincluding recurring monomers having the formulas

where each of

is individually selected from the group consisting of aliphatic and arylgroups.
 11. The structure of claim 1, wherein said crosslinked polyamicacid is formed from a polyamic acid that comprises a copolymer of adianhydride and a diamine, wherein: said dianhydride is selected fromthe group consisting of5-(2,5-dioxotetrahydrol)-3-methyl-3-cyclohexene-1,2-dicarboxylic acidanhydride, cyclobutane tetracarboxylic dianhydride,1,2,3,4-cyclopentanetetracarboxylic acid dianhydride,tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride,4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylicanhydride, bicyclo(2,2,2)oct-7-ene-2,3,5,6-tetracarboxylic dianhydride,3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride, pyromelliticdianhydride, 3,3′,4,4′-biphenyl tertracarboxylic dianhydride,2,2′-bis-(3,4-dicarboxy phenyl) hexafluoropropane dianhydride,4,4′-oxydiphthalic anhydride, 3,3′,4,4′-diphenylsulfone tetracarboxylicdianhydride, 4,4′-bisphenol A dianhydride, hydroquinone diphtaticanhydride, 3,4,9,10-perylene-tetracarboxylic dianhydride,1,4,5,8-naphthalenetetracarboxylic dianhydride, and ethylene glycolbis(trimellitic anhydride); and said diamine is selected from the groupconsisting of 1,3-bis(aminomethyl)-cyclohexane,1,4-bis(aminimethyl)-cyclohexane, 4,4′-methylenebis(cyclohexylamine),4,4′-methylene bis(2-methylcyclohexyl)amine, 3-aminobenzylamine,1,3-bis(3-aminophenoxy)-benzene, 1,3-bis(4-aminophenoxy)-benzene,1,4-bis(4-aminophenoxy)benzene, 4,4′-bis(4-aminophenoxy)-biphenyl,2,2-bis[4-4-aminophenoxy)-phenyl]hexafluproprane,bis[4-(4-aminophenoxy)-phenyl]propane,bis[4-(4-aminophenoxy)-phenyl]sulfone,bis[4-(4-aminophenoxy)-phenyl]sulfone,1,1′-bis(4-aminophenyl)-clohexane, 9,9′-bis(4-aminophenyl0-fluorene,2,2′-bis(4-aminophenyl)-hexafluoropropane, bis(2-aminophenyl)sulfide,bis(4-aminophenyl)sulfide, bis(3-aminophenyl)sulfone,bis(4-aminophenyl)sulfone, 4,4′-diamino-3,3′-dimethyl-diphenylmethane,3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether,3,3′-diaminodiphenyl methane, 3,4′-diaminodiphenyl methane,2,7-diaminofluorene, 1,5-diaminonaphthalene,4,4′-diaminooctafluorobiphenyl, 2,5-dimethyl-1,4-phenylenediamine,4,4′-ethylenedianiline, 1,3-phenylenediamine, 1,4-phenylenediamine,2,3,5,6-tetramethyl-1,4-phenylenediamine, m-xylylenediamine, andp-xylylenediamine.
 12. The structure of claim 1, wherein saidcarbon-rich layer is in the form of a pattern, said pattern comprisinglines, and said lines exhibit little, to no, wiggle.